The present invention relates to the field of mass storage devices. More particularly, this invention relates to a disc drive which includes a slider having a dual center pad with a channel or cavity located at the interface of the ceramic and alumina interface.
One of the key components of any computer system is a place to store data. One common place for storing data in a computer system is on a disc drive. The most basic parts of a disc drive are a disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc. The magnetic transducer translates electrical signals into magnetic field signals that actually record the data xe2x80x9cbits.xe2x80x9d
The transducer is typically housed within a small ceramic block called a slider. The slider is passed over the rotating disc in close proximity to the disc. The transducer can be used to read information representing data from the disc or write information representing data to the disc. When the disc is operating, the disc is usually spinning at relatively high revolutions per minute (xe2x80x9cRPMxe2x80x9d). A current common rotational speed is 7200 RPM. Rotational speeds in high-performance disc drives are as high as 10,000 RPM. Higher rotational speeds are contemplated for the future.
The slider is usually aerodynamically designed so that it flies on the cushion of air that is dragged by the disc. The slider has an air-bearing surface (xe2x80x9cABSxe2x80x9d) which includes rails and a cavity or depression between the rails. The air-bearing surface is that surface of the slider nearest the disc as the disc drive is operating. Air is dragged between the rails and the disc surface causing an increase in pressure which tends to force the head away from the disc. Simultaneously, air rushing past the cavity or depression in the air-bearing surface produces a lower than ambient pressure area at the cavity or depression. This vacuum effect counteracts the pressure produced at the rails. The opposing forces equilibrate so the slider flies over the surface of the disc at a particular fly height. The fly height is the thickness of the air lubrication film or the distance between the disc surface and the transducing head. This film minimizes the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation.
Information representative of data is stored on the surface of the memory disc. Disc drive systems read and write information stored on tracks on memory discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the memory disc, read and write information on the memory discs when the transducers are accurately positioned over one of the designated tracks on the surface of the memory disc. The transducer is also said to be moved to a target track. As the memory disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the memory disc. Similarly, reading data on a memory disc is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disc. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disc drives, the tracks are a multiplicity of concentric circular tracks. In other disc drives, a continuous spiral is one track on one side of a disc drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held accurately during a read or write operation using the servo information.
The best performance of the disc drive results when the slider is flown as closely to the surface of the disc as possible. In operation, the distance between the slider and the disc is very small; currently xe2x80x9cflyxe2x80x9d heights or head media spacing is about 0.5 micro inches. It is contemplated that smaller fly heights or head media spacing will be achieved in the future since this is one factor in achieving increased recording density.
The constant demand for increasing hard drive recording density has resulted in drastic decrease in head media spacing (HMS) over the years. Variation in the head media spacing of fly height, also termed altitude fly loss, is now an increasing source of problems due to head/media intermittent contact, especially at sub half-micro inch fly height. Intermittent contact induces vibrations detrimental to the reading/writing quality at such low fly height. Intermittent contacts may also eventually result in a head crash and total loss of data, which, of course, is very undesirable.
One source of variation in the fly height results from the alumina recession located on or near the trailing edge of the slider. Typically, the slider is formed from a wafer of silicon. The transducer or transducers (separate read and write elements) are placed onto the wafer of silicon and then encased in alumina. Once encased, the wafer is diced to form individual heads. The alumina recession is typically an inconsistent dimension for a number of reasons. This inconsistency between various heads leads to inconsistency in fly heights or pole tip fly heights which leads to inconsistent results during reading and recording of information representing data.
In addition, the interface between the alumina and the substrate typically includes the closest point between the slider and the disc when the slider is passing over the surface of the disc in transducing relation. As a result, if there is any variation in the fly height, this closest point is a likely contact point between the slider and the disc.
What is needed is a slider air-bearing design for low altitude sensitivity. What is also needed is a design for controlling the alumina recession so that it is less variable and more consistent. In addition, there is a need for a slider air-bearing design that moves the closest point to another area of the slider so that in the presence of fly height variance, there will be more leeway before contact between the slider and the disc. The result is more consistent read and write performance characteristics amongst the heads in a disc drive as well as a design that is not as sensitive to the amount of alumina recession at the interface between the alumina and the slider.
An information handling system, such as a disc drive, includes a base, a disc stack rotatably attached to the base, and an actuator assembly movably attached to the base. The actuator assembly also includes a load spring and a slider attached to said load spring. The slider has an air-bearing surface. The air-bearing surface includes a leading edge, a trailing edge, and a center pad positioned near the trailing edge. A transducer is positioned within the center pad. The center pad has a channel or cavity therein. The channel or cavity is substantially parallel to the trailing edge. The channel or cavity positioned near the transducer. The center pad includes a substrate portion, and a portion covering the trailing edge of the slider which substantially encapsulates the transducer. A transition portion is located between the substrate portion and the portion covering the trailing edge. The channel or cavity is positioned near or at the transition portion. In one embodiment of the invention, the channel or cavity has a depth substantially equal to the height of the center pad. The cavity or channel substantially splits the center pad into a first center pad portion, and a second center pad portion. The first center pad portion is located toward the leading edge, and the second center pad portion is located toward the trailing edge. In some embodiments, the width of the channel or cavity is controlled to control the amount of pressure produced by the second center pad portion. In other embodiments, the dimensions of the channel or cavity are controlled to control the amount of movement between the substrate portion of the slider and the portion covering the trailing edge of the slider which results from annealing the slider. The air-bearing surface also has a first side rail located between the leading edge and the trailing edge, and a second side rail located between the leading edge and the trailing edge. The invention includes the slider as well as the slider in combination with the disc drive.
Advantageously, slider having a dual center pad with a channel or cavity having an optimized width X has low altitude sensitivity. The design controls the alumina recession so that it is less variable and more consistent. The slider air-bearing design also moves the closest point to another area of the slider so that in the presence of fly height variance, there is more leeway before contact between the slider and the disc. The result is more consistent read and write performance characteristics amongst the heads in a disc drive as well as a design that is less sensitive to the amount of alumina recession at the interface between the alumina and the slider.